System prompt

A system prompt is the standing instruction you give an AI that frames every reply, who it is, how it should behave, what it knows about your business, and the rules it must always follow. Unlike a one-off message, it sits above the conversation and shapes everything the model does in that session. It's where you set role, tone, constraints, and context.

For a founder this is the cheapest, highest-leverage lever on an agent's behaviour. Most of the difference between a generic chatbot and one that sounds like your company, knows your policies, and stays in its lane comes from a well-written system prompt, not a fancier model. It matters because it's also where reliability lives: a vague prompt produces vague, off-brand, occasionally reckless output. Spell out the role, the boundaries, and what to do when unsure, and you've done most of the work of making an agent trustworthy before writing a line of code.